Cool ! Thanks
However, I see some comical irony buying super-quiet transistors from a company whose stock in trade is distortion products ;-)
@Toys4Boys - for 2 Ohms I'd try settings between 20-40, then ramp it up towards 100. It will likely get better and better than trail off to worse sounding. You'll have to find that sweet spot.
The build guide doesn't have every permutation for the switches. Here's a little more granularity running up to 100 Ohm you can try.
1 = switch ON. 47k is always on. It's fixed in the circuit.
There is a TON of info on MC SUTs here:
http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html
There are great MC SUT calculators here:
http://mh-audio.nl/Calculators/StepUpTransformer.html
Which Rothwell do you have? It looks like they have multiple models with different ratios.
For fine tuning you can calculate a resistor to put in parallel to the 47k on a MM phono stage that optimizes cart, MC SUT, and the MM Preamp. That's what those calculators help you figure out.
The build guide doesn't have every permutation for the switches. Here's a little more granularity running up to 100 Ohm you can try.
1 = switch ON. 47k is always on. It's fixed in the circuit.
There is a TON of info on MC SUTs here:
http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html
There are great MC SUT calculators here:
http://mh-audio.nl/Calculators/StepUpTransformer.html
Which Rothwell do you have? It looks like they have multiple models with different ratios.
For fine tuning you can calculate a resistor to put in parallel to the 47k on a MM phono stage that optimizes cart, MC SUT, and the MM Preamp. That's what those calculators help you figure out.
Rothwell MCX, unlikely that I will use that once I've built my P3. I needed the MCX to play into my Naim SN3.
WBS, that part number will work. It's on-on. Wire to the center and one of the outer terminals. Good to go.
I'm using an amazon special SPST in mine. One of these.
https://www.amazon.com/gp/product/B01M3261RL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
https://www.amazon.com/MTS-101-Posi...trial&sprefix=spst,industrial,116&sr=1-5&th=1
It seems you haven't read the Quasimodo document yet, or analyzed the circuit diagram of a Quasimodo tester. I recommend you read page 3 of the doc and then study the schematics attached to post #1 of the QM thread. Eureka!
@GKTAUDIO and @Mark Johnson Quasimodo would certainly not pose any problems by design, assuming no construction errors and no Murphy.
Adding a Quasimodo-measured snubber to a MC Step-Up transformer would be wildly detrimental to the audio performance.
Quasimodo's ideal snubber value is made to damp any ringing of the transformer at AC mains full-wave rectified switching frequency. Which is to say 120 or 100Hz.
A moving coil SUT is a teeny, delicate, and highly permeable transformer made to work with very small signals at full audio range, and where those signals are not at equal amplitude. (Remember the RIAA curve pressed into the disc has very low bass (so the needle doesn't jump out of the groove) and very high treble (so there's actually something to "read"))
This means that the signal must make it through the SUT as unmolested as can possibly be. IF there is a snubber or some kind of loading resistor on the secondary of the SUT, it's got to be tuned to the specific transformer's own capacitance and leaking inductance, and you could certainly do a Quasimodo-style thing that way, but you'd use a test record and a scope, with the cartridge itself as generator, etc... Were you to use Quasi, two problems would crop up - 1) it's not tuning for the right frequency(ies) and it's an ENORMOUS signal that it injects into DUT. 9000mV. !! (A typical MC is 0.5mV or so). You'll hammer the everliving crud out of the jewel-like phono transformer.
Anyway, read this, it's the absolute best document on Step Up Transformers on the internet.
http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html
speaking of SUTs, practically, all one need is decent 2-channel (some call it stereo) 100KLin pot (wired as variable resistance), connected in place of usual 47K loading resistor, few bottles of nice wine and few days of nice and cozy listening
then, when settled on pot position, 20secs with ohmmeter to determine what's pot set at, and Voila!
then, when settled on pot position, 20secs with ohmmeter to determine what's pot set at, and Voila!
If I get what you are suggesting, thanks for not going all out zenglish! By using the 100KLin I could maximize the loading for the specific cartridge, the only issue there is that I have a stable of cartridges, growing all the time, and this would necessitate putting the 47K back in place of the pot?
I should add very clever idea, but one expects nothing less from ZM!
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There seems to be an assumption here that bears clarification, I have read various opinions re. SUT or additional gain in the phono stage w/ appropriate settings options. I suspect that @wayne designed a pretty awesome phono minimizing potential noise issues, I am interested in doing the comparison for myself! Also the Rothwell tx in the MCX, Lundahl ?, is not likely the better model, ll1931.
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Be cautious with the pin numbers 1 2 3, D S G on the 2SK209 adaptor it is different than the numbers on the P3 PCB 1 2 3, D G S.
Pa Pa, uses that method with switched resistors to find the JFET distortion sweet spot. (think decade box, you can set the switches like the stops on an organ for the flavor of the day)
The wine is the costly part, it causes errors.
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not good enough, not just because of resistive material and critical contact but also because of necessary included (antenna) additional length of wires to pot
pot is good solution for fine and easy tune, without too much brain engagement (as is necessary with dip switches)
now - for quick change - either 1pin holders for loading resistor(s) or dip switches ( as Wayne devised for Pearl 3)
I was merely speaking about pot used as simple and no brainer tool.
Very, very doubtful. At this point the only boards in the wild are those that were given away at BAF. Perhaps somebody who was there who isn't intending on building would be willing to move them along.